Why drivers like neogeo cps1 cps2 have frequency below 60HZ?
This is a bad thing, because the games do not have a smooth scroll ... example: the neogeo in the current mame has its frequency at 59.18HZ, but the correct would be 60HZ!

Those games used monitors back in the day that were capable of those frequencies. Anyways, several games that say 60hz aren't actually 60hz iirc, and I think I heard monitors these days aren't really 60hz as well using a refresh rate that just gets rounded up to 60.

The problem of mame current is that because the frequencies of most games are below 60hz, they do not flow smoothly ... example of this is the neogeo driver that has a frequency of 59.18hz, the games choke slightly, because there is no synchrony with monitors 60hz.

The old mame up to version 0.100 for neogeo and 0.112 for cps1 and cps2 were all in 60hz, and flowed perfectly smooth without gagging!

My suggestion is that the developers of the mame add a choice of 60hz!
It does not cost anything to add this option.

They are not going to do that because that is not what those games were programmed for or how they're meant to be displayed in. If you want a smoother display, you have your choice of triple buffer, sync refresh, or wait vert sync. There's also something called g-sync with nvidia cards that should allow for display of different refresh rates without tearing. If you really to want have the games play at 60hz, enable cheats and set the refresh rate yourself in the sliders tab or compile your own version of mame.

Mame time has all the power in the hands, so do not do it because you do not want.

Sliders do not allow you to change the frequency accurately ... because it changes only the first 2 digits ... and also does not allow saving configuration.

So that mame time added this option in sliders, if it is not possible to change the frequency accurately, nor is it possible to save the configuration made?

Since it has an option in sliders, why not improve it adding precision in the choice of frequency and allowing to save the configuration in archive .CFG?

It would appear the only way to change to exactly 60Hz it is to adjust the source file(s) to assign the Hz to exactly what you want, then.
MAME is only concerned about proper refresh rates reflected in the pcb's raw parameters including pixel clock speed, vblank/Interrupt timers and other settings to accurately reflect the emulated Hz. Sadly, you'll get no help with it from the official forums.. perhaps a derivative build may be interested in helping.